Solve the system of equations. $\begin{aligned} &7x+10y = 36 \\\\ &y=2x+9 \end{aligned}$ $ x=$
Explanation: We are given that $ y = {2x+9}$. Let's substitute this expression into the first equation and solve for $x$ as follows: $\begin{aligned} 7x+10{y}&=36\\\\ 7x+10\cdot({2x+9})&=36\\\\ 7x+20x+90& = 36\\\\ 27x&=-54\\\\ x&=-2 \end{aligned}$ Since we now know that $ x={-2}$, we can substitute this value into the second equation to solve for $y$ as follows: $ \begin{aligned} y &= 2\cdot {x}+9 \\\\ y&=2\cdot({-2})+9\\\\ y&=5 \end{aligned}$ This is the solution of the system: $\begin{aligned} &x = -2 \\\\ &y=5 \end{aligned}$